1. Technical Field
The present invention relates to optical communications, and in particular, to a system and method for providing a multi-wavelength transceiver device with integration on transistor-outline (TO) headers.
2. Related Art
Wavelength Division Multiplexing (WDM) has become the dominant technology for transmitting data at high rates over long spans of optical fiber. A typical WDM system comprises expensive single-mode thermoelectrically stabilized lasers, external-cavity modulators, and single-mode fiber. In this system, light of different wavelengths is typically multiplexed and demultiplexed using expensive arrayed waveguide gratings (AWGs). As the desire for increased bandwidth penetrates the local access and metro markets, it has become imperative to find cost-effective solutions for providing high data rates over multi-mode fiber (MMF) that has distances less than 300 m. Cost is usually the most important metric for comparing different solutions that meet the specifications of a particular optical link. It is well known that a 10 Gbps serial solution using an inexpensive vertical cavity surface-emitting laser (VCSEL) source cannot be used on the existing MMF base because the 160 MHz km modal bandwidth of the fiber limits transmission at this rate to distances less than 32 m. At 1310 nm, where the modal bandwidth of installed MMF is 250 MHz km, the maximum distance is extended to 50 m, still short however of the desired 100 m span.
A current task force investigating 10 GBase Ethernet considers a four-channel WDM, using a course wavelength grid spacing as an important physical medium dependent (PMD) layer option for deployment of this new standard. Systems based on a coarse wavelength spacing near 20 nanometer, in contrast to a 0.8 nanometer spacing for conventional WDM, are insensitive to laser frequency drift with temperature, eliminating the need for thermoelectric controllers. Advances in the fabrication techniques of vertical cavity surface-emitting lasers (VCSELs) at wavelengths near 850 nm present a low-cost alternative to much more expensive distributed feedback (DFB) lasers at 1550 nm, particularly when the course wavelength spacing permit higher production yields. In further contrast to conventional WDM, the use of multimode fiber permits passive optical alignment of optical components, reducing cost even more and enabling first generation 10 Gbase Coarse Wavelength Division Multiplexing (CWDM) systems to be deployed in spans up to 100 m over the existing MMF base. For example, a four-channel CWDM PMD at 850 nm, each channel operating at only 2.5 Gbps, has a transmission distance up to 128 m on installed MMF. This meets the optical link specification of 100 m.
Several different four-channel transceiver designs have been currently proposed. One such transceiver design uses a 4-way optical splitter and thin film filters (TFFs) to demultiplex the signals, and is based on VCSELs at center wavelengths in the 820-865 nm range with 15 nm spacing. Another transceiver design is also based on TFFs and VCSELs in the same wavelength range but utilizes a polymer waveguide in xe2x80x9czig-zagxe2x80x9d configuration to reduce loss by 6 dB per channel over the 4-way optical splitter design. There is also a design that builds upon the polymer waveguide structure and utilizes un-cooled DFB lasers in the 1280-1340 nm range and 20 nm channel spacing. However, none of these transceiver designs utilizes a method to achieve high levels of integration, so as to lower the cost of manufacturing these transceiver devices. As a result, the manufacturing cost remains high. Therefore, an arrangement that is suited to the implementation of a low cost CWDM transceiver is needed.
Other problems also exist in the current conventional transceiver designs. For example, the thin film filter (TFF) designs in the conventional transceiver designs are not optimized for non-normal incidence, which is known to produce a shift in the wavelength in passband and cause s and p polarization dependence. In addition, close proximity of detectors and transimpedance amplifiers associated with different channels exist in these transceiver devices. As a result, these devices are vulnerable to channel xe2x80x9ccross-talk.xe2x80x9d Channel-dependent optical loss in both the transmitter and receiver often leads to unequal signal strengths.